Metallothionein Genes in the Nematode Caenorhabditis elegans and Metal Inducibility in Mammalian Culture Cells

Genomic DNAs of metallothionein I and Ⅱ in Caenorhabditis elegans(CeM-I and CmMT-Ⅱ） were isolated by YAC library/polytene filter hybridization followed by subcloning of corresponding cosmid clones.Both enes are mapped at chromosome V.Although the similarities of 5‘-flanking regions and coding regions have shown only 55-58%,the mtrons are split at the same position in both genes,indicating that these two genes are originally from the same gene.While several metal responsive elements are conserved among eukaryotes,only one metal responsive element was found in the promoter region in CeMT-Ⅱ and not in CeMT-I.Indeed,neither of 5‘-flanking regions of CeMT-I nor CeMT-Ⅱ connected to chloramphenicol acetyltransferase reporter gene is responsive to heavy metals in mammalian culture cells by transient transfection analysis.These results would suggest that the metal regulatory factors in C.elegans might be different from those conserved in invertebrates and vertebrates,although the MTs in C.elegans reveales the similarities to mammalian MTs in several points.